Electrically set mechanical time fuse



June 5, 1951 G. J. WATT 2,555,384

ELECTRICALLY SET MECHANICAL TIME FUSE Filed Jan. 14, 19.48

GORDON JAMES WATT Patented June 5, 1951 Gordon J. Watt, Yonkers, N. Yr

Application January 14, 19 48, Serial No. 2,187

(01. 89-1) 7 (Granted under the act of March 3, 1883, as

1 Claim.

amended April 30, 1928; 3'70 0. G; 757) This invention relates in' general to electrical means for controlling the operation of a mechanical time fuze, and more particularly to magnetic means for controlling the operation of the timing element of the fuze.

In the prior art the mechanical time fuse contains a timing element generally designated as the clock, which has an escapement mechanism for determining a time interval. Setting means are provided on the outer surface of the projectile such as a rotatable nose, for determining the desired time interval. This interval is determined by a mechanism on the gun called the fuzesetter, in order to cause the projectile to burst at a predetermined range.

When firing on slow moving targets this system functions reasonably well and many direct hits are recorded, but when used on fast moving targets such as airplanes it fails to function properly because the timing is inaccurate. In other words the projectile cannot be made to burst close enough to the airplane to cause damage from the burst.

Applicant has discovered that by setting the time as the projectile leaves the gun, much more effective firing can be obtained. The apparatus for accomplishing this act is disclosed in detail in the body of the specification.

One of the advantages arising from this invention results in continuously setting the time as the projectile leaves the gun, a very desirable procedure when the target is continuously tracked. Other advantages are the reduction of initial velocity errors and the elimination of dead-time errors on time settings. 1

Accordingly, it is an object of this invention to vary the time setting of a mechanical time fuze by electrical means.

Another object is to vary the time setting of a mechanical time fuze by electrical means as it leaves the gun.

Another object is to vary the time setting of a mechanical time fuze by electrically altering the forces operating upon the timing mechanism as the projectile leaves the gun.

Another object of the invention is to carry out the steps of an improved method of accurately setting the fuses of explosive projectiles prior to firing.

Another object is the provision of a fuze which will be economical to manufacture, reliable in operation and which possesses all of the qualities of ruggedness and dependability in service.

Fig. 1 illustrates the gun with the electrical means for controlling the time setting oi the pro jectile mounted thereon;

Fig. 2 is an elevational view of a projectile, partly in section; and

Fig. 3 is a sectional view of the projectile along line 33 illustrating how the electrical means operates upon the escapement.

As illustrated in Fig. 1, the setting of the time of the fuze is accomplished by an exciting coil surrounding a section of the path of the projectile. When an electric current is passed through the exciting coil a magnetic field is established through which the projectile must pass as it leaves the muzzle of the gun In order to secure the coil against the direct action of the propulsive gases, the latter are preferably deflected laterally between the muzzle and the deflecting coil, this being obtained by mounting a muzzle brake l on the gun barrel 2 in a manner described in U. S. Patent 1,739,921. The exciting coil 3 is mounted on the cylindrical portion ll, located in front of the baflle wall 5, of the muzzle brake, and is connected through a regulating resistance 6 and ammeter l to a source of current 8- such as a battery. The regulating resistance serves to vary the current supplied to coil 3 and thus varying the strength of the magnetic field produced by the current in the coil. A second regulating resistance 9 may further be provided in order that the current strength may be instantaneously changed by throwing switch [0 instead of regulating the rheostat.

In operation, a mechanical time fuse of the type described in the U. S. patent to Junghans 1,266,687, is modified by the addition of an electromagnet for varying the period of the escapement and may be given a fixed setting, for example 2,000 yards. This means'that without any current flowing in coil 3 of the electromagnet, the projectile will burst when it has traveled 2,000 yards from the gun. It may also be assumed for this discussion that with maximum current flowing in coil 3 the projectile will burst at 1,000 yards from the gun because the electromagnet aids the restoring'force of the-balance spring of the escapement mechanism, If the projectile explodes at 2,000 yards with no current in the coil and at 1,000 yards with maximum current in the coil, it is clear that the exploding may be regulated between 1,000 and 2,000 yards by varying the value of the current in coil 3. It will be shown in a discussion of Fig. 2 that the time setting of the fuze is proportional to the value of the current in coil 3. If the target is continuously tracked the time setting may be made continuously by calibrating the current in terms of range and regulating it accordingly. Obviously, much lost motion and errors resulting from the fuzesetting of the prior art are eliminated by the apparatus of this invention in setting the mechanical time fuze electrically, thus improving the efiectiveness of the firing of the gun. It may be said that the fuze setting .of .the prior art 5 which was designed for effective firing in two dimensions (on the ground) fails to be efiective when used in three dimensions such as aircraft. in flight.

It has been observed that certain material exhibits a residual magnetism variable in accordance with the magnitude of the magnetometive force to which the material has been or is subjected. Accordingly, ith noreis of Tthe electromagnet is fabricated of such material selected so that it has the proper magnetic retentivity. In this respect the material is'-referred to as being a permanent magnet since it is subject to permanent magnetization.

. iEigiz-illustrateshow the time of the'fuze in the projectile is changed when under the influence of current flowing incoil 3 of Fig. 1. The projectile has-a softiron nose i I which forms the core for secondary-coil H. The terminals IA and I5 'of-secondarycoillz areconnectedtofield coil l3 of 'electromagnet l-6-I-3, which held coil produces the magnetomotive force to which the core material is subjected which magnetomotive force is proportional to the current flowing in the :field coil.

At the base of soft iron :nose II and coil l2 is located the mechanical time -fuze l8, of the type described by the U. 8. ,Patent No. 1,266,687, modified to the extent thatelectromagnet Iii-46 may be so located that the escapement lever or balance [1! forms a'portionof the magnetic cir cuit of the 'electromagnet with a small air gap.

The escapement'is biased by a spring 20 which exerts'a constant series-of forces repeated in the cyclic movement of theescapement lever I! as it l0 operates upon the ratchet wheel 23'. "This constant effect gives a definite time period for the operation of the escapement and ratchet. The timeof operation of the escapement and ratchet maybevaried bythe addition of a magnetic force applied' to the balance or lever I! force. It has been assumed for purposes :of discussion that the two'elements'which determine the-periodareadditive and that the application of the magnetic forces decrease the time required to ignite the fuse;

Fig. 3 is an end view of the mechanical fuse with the electromagnet shown in section illustrating the relation of the escapement lever, ratchet wheel and electromagnet. 7 In operation the mechanical time fuze is given a fixed setti ng, assumed to' be'2,000 yards, before placing the projectile in the .gun. When the target 'approachesto 2,000 yards firing is begun, arid as the target is continuously tracked the range is setby varying the current to coil '3 of Fig. 1 continuously as the 'range changes. This may bedone by the'opera'tionof variable resistrent in 0011 3;

ances 6 and 9, and the range may be calibrated directly by an ammeter I for convenience of operation. This variable current, proportional to the range, in coil 3 sets up a magnetic field through which projectile 24 passes whenit leaves the gun. The speed of the projectile carrying coil l2 through the magnetic field set up by coil 3, induces a voltage and a corresponding current in coil l2 proportional to the value of our- The current of coil l2 passes through the coil l3 of electromagnet I3l6 setting up a magnetomotive force magnetizing the core It. This core material, because of its ability to retain at least a portion of the induced magnetism, maintains a magnetic field acting upon the balance I! of the escapement mechanism thereby altering the time of operation of the escapement variable in accordance with the magnitude of the current in coil 3 and variable also in accordance with the range set upon instrument 1. In this manner the projectile may becaused to burstmuch more-closely to the target and the efiectiveness of the firing greatly increased.

The invention herein described may be manufactured and used byor for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

In combination a projectile having an ogive portion formed of magnetically permeable material recessed to receive a first winding having its outer surface conforming generally with said ogive, a mechanical time fuze contained within said projectile having an escapement assembly including a magnetically permeable oscillating member, a magnetic field structure comprised of magnetically retentative material having poles defining an air gap, said field structure being positioned adjacent said oscillating member so that the period of oscillation thereof will be influenced by the magnetic field in said air gap, a second winding on said field structure connected inshunt' with said first winding, and means for inducing a predetermined voltage in said first winding on discharge of said projectile from a gun to control the field strength in said air gap whereby to alter the timing of-said-fuze.

GORDON JAMES 'WAT'I.

REFERENCES CITED The following referencesarc of record in the file of this :patent:

UNITED STATES PATENTS Number Name Date 1,266,687 Junghans May 21, 1918 1,739,921 Schuler et al Dec. 17, 1929 2,061,047 Schweitzer Nov. 17, 1936 2,359,656 Lurtz Oct.'3, 1944 2,465,351 Busignies et a1. Mar. 29, 1949 

